Verifying Greenhouse Gas Verifying Greenhouse Gas Emissions: Methods to Emissions: Methods to

Support International ClimateSupport International Climate AgreementsAgreements

Stephen PacalaMarch 16, 2010

Committee Members

Stephen Pacala, (Chair), Princeton UniversityClare Breidenich, Independent ConsultantPeter Brewer, Monterey Bay Aquarium Research InstituteInez Fung, University Of California, BerkeleyMichael Gunson, Jet Propulsion LaboratoryGemma Heddle, Chevron CorporationBeverly Law, Oregon State UniversityGregg Marland, Oak Ridge National LaboratoryKeith Paustian, Colorado State UniversityMichael Prather, University of California, IrvineJames Randerson, University of California, IrvinePieter Tans, National Oceanic and Atmospheric AdministrationSteven Wofsy, Harvard University

NRC Staff: Anne Linn

Context for the Study

• Anthropogenic greenhouse gases are accumulating in the atmosphere

• International agreements to limit future greenhouse gas emissions will rest on the ability of each country to estimate emissions accurately and to monitor and verify changes over time

Scripps CO2 program

Committee Charge and Focus

Charge: Review current methods and propose improved methods for estimating and verifying greenhouse gas emissions at different spatial (e.g., national, regional, global) and temporal (e.g., annual, decadal) scales.

The committee focused on the gases, methods, and scales relevant to international climate agreements– National, annual emissions and decadal trends– Public domain information

Greenhouse Gases Covered

• Carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), sulfur hexafluoride (SF6), chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), and perfluorinated hydrocarbons (PFCs)– result from human activities– long lifetimes in the atmosphere – currently included in international agreements

• Particular focus on CO2

– largest single contributor to global climate change

Bottom Line• National fossil-fuel CO2

emissions can be estimated by each nation accurately enough to support a climate treaty (error <10%).

• Strategic investments could enable accurate independent checks on self-reported estimates of CO2 emissions from fossil fuel and deforestation within 5 years (<10% for critical countries)

• Estimates of emissions of other greenhouse gases will remain uncertain in the near term

IPCC (2007)

One-quarter of countries are responsible for 80% of global

emissions

Methods for Estimating Emissions

• UNFCCC National inventories – Estimates anthropogenic emissions and removals

(sinks)– Based on measurements of human activities

• Tracer-transport inversion – Estimates net anthropogenic and natural sources and

sinks – Based on atmospheric and/or oceanic measurements

of the gases and models of air and water flow • Land-use measurements and models

– Estimates emissions and sinks of CO2, CH4, and N2O – Based on land cover information from satellite imagery

and biogeochemical models

UNFCCC Inventory

Emission = Activity Level X Emissions Factor

(i.e. steel prod.) X (CO2 per unit prod.) Current error:

<10% for CO2 from developed countries but up to 50% for CH4 and 100% or more for N2O, CFC’s, PFC’s, HFC’s and SF6.

Methods for Estimating Emissions

• UNFCCC National inventories – Estimates anthropogenic emissions and removals (sinks)– Based on measurements of human activities

• Tracer-transport inversion – Estimates net anthropogenic and natural sources and

sinks – Based on atmospheric and/or oceanic measurements

of the gases and models of air and water flow • Land-use measurements and models

– Estimates emissions and sinks of CO2, CH4, and N2O – Based on land cover information from satellite imagery

and biogeochemical models

CO2 SamplerLANDCO2 Sampler

Prevailing Wind

CO2

Tracer-Transport InversionCurrent errors of 100% or more for all gases.

Fossil-fuel CO2 Emissions

Problems with Tracer Transport Method

• Transport Error• Large and incompletely understood

background fluctuations of natural emissions.

• Current sampling grid avoids urban areas and large industrial sources which generate most emissions.

• Current sampling grid is too sparse.

Atmospheric Sampling Network

Methods for Estimating Emissions

• UNFCCC National inventories – Estimates anthropogenic emissions and removals (sinks)– Based on measurements of human activities

• Tracer-transport inversion – Estimates net anthropogenic and natural sources and sinks – Based on atmospheric and/or oceanic measurements of the

gases and models of air and water flow • Land-use measurements and models

– Estimates emissions and sinks of CO2, CH4, and N2O – Based on land cover information from satellite imagery

and biogeochemical models

Methods for Estimating Emissions

Models convert changes visible in the imagery into carbon emissions

Errors up to 100% or more for all gases.

Categories of Recommendations

• Strengthening national greenhouse gas inventories

• Improving independent estimates of fossil-fuel CO2 emissions

• Improving independent estimates of fluxes from land-use sources and sinks

Current Differences in Estimating and Reporting Emissions

• Developed countries– Produce annual estimates of sources and sinks of

6 greenhouse gases– Use the most rigorous methods → most accurate– UNFCCC review of methods and data sources

• Developing countries– Make periodic estimates of CO2, CH4, and N2O

(many countries have produced only 1 inventory)– Use simplest methods → least accurate– No UNFCCC review

Recommendation

UNFCCC parties should strengthen self-reported national emissions inventories by working toward

• Extending regular, rigorous reporting and review to developing countries

• Extending top-tier (most stringent) IPCC methods to the most important greenhouse gas sources in each country

This would reduce errors to <10% for CO2, and, depending on the country, from <10% to 50% for CH4, from 10% to 100% for N2O, and from <10% to 50% for the fluorinated gases.Financial and technical assistance will be required to help developing countries collect, analyze, and report emissions regularly.

Recommendation

Annex I (developed) countries should develop and implement standardized methods for preparing and publishing inventories that are gridded at spatial and temporal resolutions appropriate for the particular greenhouse gas and source

• UNFCCC inventories report annual, national totals, even when more detailed information is collected

• Gridded inventories would facilitate independent checks using atmospheric data and models

Categories of Recommendations

• Strengthening national greenhouse gas inventories

• Improving independent estimates of fossil-fuel CO2 emissions

• Improving independent estimates of fluxes from land-use sources and sinks

Improving Independent Estimates of Fossil-Fuel CO2 Emissions

• Deploy a CO2-sensing satellite

• Establish new atmospheric sampling stations (ground, ocean surface, aircraft) in strategic locations

• Measure 14C in the CO2 samples already being collected

Recommendation

NASA should build and launch a replacement for the Orbiting Carbon Observatory (OCO)

• Most fossil-fuel CO2 emissions emanate from large local sources

• OCO’s high precision and small sampling area could detect these signals and attribute them to the emitting country

• Demonstrate the capability for monitoring CO2 from space for a climate treaty– Improve lifetime and coverage in future designs

Comparison of Satellite Capabilities

Example: 500 MW coal power plant

4 Mt CO2 yr-1

3 m s-1 OCO GOSAT

Instrument accuracy

1-2 ppm 4 ppm

CO2 in air

sampled

1.7 ppm 0.4 ppm

CO2 signal would be detectable by OCO, but not by GOSAT (best available satellite)

Recommendation

Extend the international atmospheric sampling network:

(1) to research the atmospheric “domes” of greenhouse gases over a representative sample of large local emitters, such as cities and power plants

• Existing stations are located away from cities and power plants to study natural sources and sinks

• New measurements at locations radiating from the center of selected large emitters would:– Document shifts in fuel sources in urban areas– Provide data to calibrate satellite measurements – Demonstrate a ground and aircraft monitoring capability

Recommendation

Extend the international atmospheric sampling network:

(2) to fill in underrepresented regions globally, thereby improving national sampling of regional greenhouse gas emissions.

• Stations are capable of accurately detecting widespread, unconcentrated sources

• New stations in high-emitting countries would improve tracer-transport modeling → improve independent verification of emissions

• More frequent vertical profiles would constrain atmospheric transport → improve comparisons with satellite CO2 measurements

Recommendation

Extend the capability of the CO2 sampling network to measure atmospheric 14C

• Natural emissions of CO2 fluctuate and can be as large as fossil-fuel sources

• CO2 from fossil-fuel and non-fossil-fuel sources can be differentiated using radiocarbon (14C) measurements – Modern organic material contains 14C from cosmic rays and

bomb tests, but the 14C in fossil fuels has decayed away

• Measurements could be made in CO2 samples that are already being collected at low cost

Problems with Tracer Transport Method

• Transport Error• Large and incompletely understood

background fluctuations of natural emissions.

• Current sampling grid avoids urban areas and large industrial sources which generate most emissions.

• Current sampling grid is too sparse.

Accuracy of Fossil-fuel CO2 Emissions Estimates

Sector or Activity Method

Current Uncertainty

Uncertainty of Improved Methods

Fossil-fuel combustion

UNFCCC inventory

<10-25% (developed countries)

<10% (all countries)

Fossil-fuel combustion

Atmospheric measurements and models

50->100% <10-50% (annual)

<10-25% (decadal)

Large local sources

Atmospheric measurements and models

>100% 10-25% (annual)

<10% (decadal)

Categories of Recommendations

• Strengthening national greenhouse gas inventories

• Improving the ability to independently estimate fossil-fuel CO2 emissions

• Improving independent estimates of fluxes from land-use sources and sinks

Improving Independent Estimates of Land-Use Emissions and Sinks

• Produce global maps of land-use and land cover change

• Design a research program to improve methods for estimating AFOLU emissions

Recommendation

Establish a standing group to produce a global map of land-use and land cover change at least every 2 years. This will require a commitment to maintaining the continuous availability, in the public domain, of Landsat (or an equivalent satellite) and high-resolution satellite imagery.

• Frequent mapping necessary to detect important changes (e.g., forest clearing or planting)

• Provide an independent check on dominant sources of AFOLU CO2 emissions

• Enable more accurate land-use emissions reporting from developing countries

Global maps• Based on Landsat

– Publicly available, medium resolution

• Supplemented with targeted high-resolution imagery to monitor logging, forest degradation, and some agricultural practices (e.g., rice cultivation)

NASA Earth Observatory

Recommendation

An interagency group, with broad participation from the research community, should design a research program to improve and, where appropriate, implement methods for estimating agriculture, forestry, and other land-use emissions of CO2, N2O, and CH4

• Research to make more accurate estimates of AFOLU emissions– Emission factors: CO2 from deforestation and forest degradation, CH4

from rice paddies and cattle, and N2O from fertilizer application– Natural cycles of CO2, CH4, and N2O

• Supporting observations, including flux measurements and ecosystem inventories (annual measurements of major carbon pools)

• Improved methods could become part of UNFCCC reporting

Accuracy of AFOLU CO2 Emissions Estimates

Sector or Activity Method

Current Uncertainty

Uncertainty of Improved Methods

AFOLU UNFCCC inventory

<10-100% (developed countries)

<10-50% (all countries)

AFOLU Land-use measurements and models

10-100% 10-50%

Deforestation source, afforestation sink

Land-use measurements and models

10-100% (forest area)

25-100% (emissions)

<10-25% (forest area)

10-25% (emissions)

Implications for Climate Agreements

Implementing the recommendations would

• Establish rigorous annual inventories for all countries as the core of a greenhouse gas monitoring system

• Enable independent checks (<10% accuracy) on fossil-fuel combustion and deforestation, which are responsible for three-fourths of UNFCCC greenhouse gas emissions

• Improve monitoring and verification of all greenhouse gases through targeted research

Simplifying the Monitoring and Verification Problem

90% of global emissions are from energy and AFOLU (agriculture, forestry, and other land use) → obvious focus for monitoring and verification